The present invention relates to a process of removing flue gas cleaning residues during the wet cleaning of flue gases in a combustion system having a hot gas filter and washers The present invention also relates to an apparatus for implementing the process.
In the operation of typical flue gas cleaning systems, acids and other contaminants present in the flue gas are precipitated in the washing liquid In order to keep the washing liquid functioning and to allow it to be discharged into the environment, the washing liquid is generally neutralized by the addition of a caustic soda solution or lime. This causes the wash water or washing liquid to be enriched in salts. To prevent crystal formation in this water, the salt enrichment must not exceed 22 to 25%. However, the removal of such concentrates poses problems since, due to the contaminants contained therein, only a limited amount of them can be added to normal waste waters.
This is even more of a problem in systems which are used to combust radioactive substances. In such systems, the concentrates can be put into permanent storage in solidified form, but the additional development of secondary waste is considerable. Some known concentrate drying processes have tried to pulverize the material to be dried to the greatest extent possible. However, this still requires an additional drying step which consumes additional energy. Other known processes, such as, for example, vacuum drying or drying by means of infrared or microwaves consume large amounts of energy and require a separate process step. Therefore, there exists a need for a simple process which consumes relatively little energy.